ML20024E516
| ML20024E516 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 08/09/1983 |
| From: | Garrity J Maine Yankee |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| JHG-83-202, MN-83-167, NUDOCS 8308150211 | |
| Download: ML20024E516 (2) | |
Text
,
MAIRE 3p@HAllHEE Atom /CPulVERCOMPARU*
,uougr,j,in"gy3l (207) 623-3521 O
August 9, 1983 MN-83-167 JHG-83-202 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Mr. Robert A. Clark, Chief Operating Reactors Branch No. 3 Division of Licensing
Reference:
(a) License No. DPR-36 (Docket No. 50-309)
Subject:
Thermal Shicld
Dear Sir:
This letter is in response to a request from your staff to submit additional information regarding the Maine Yankee thermal shield.
During the last refueling outage a complete inspection of the thermal shield was conducted by removing the core barrel. The only indications of wear noted were on three of the nine top positioning pins which were dislodged. Wear indications and radiation levels on the pins indicate the dislodgement was not recent. During the next refueling outage, we plan to remove the core barrel and conduct another thorough inspection of the thermal shield.
We have completed an initial evaluation of the thermal shield support system integrity using the loose parts monitoring system and neutron noise analysis techniques. Our consultants, who have extensive experience in similar monitoring programs, have concluded that there is no evidence of increased thermal shield movement since our last inspection. Based on the results of this analysis, we have concluded that the Maine Yankee thermal shield support system is not experiencing any significant degradation.
For the remainder of this operating cycle, we will closely monitor the reactor vessel loose parts system and periodically check neutron noise to assure that abnormal thermal shield movement is not occurring. If we have evidence of any significant degradation in the thermal shield support system, we plan to shut the plant down for a thorough inspection.
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8308150211 830809 PDR ADOCK 05000309 Y
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United States Nuclear Regulatory Commission August 9, 1983 Attention: Mr. Robert A. Clark, Chief MN-83-167 We have completed a preliminary evaluation of the consequences of a postulated failure of the thermal shield support system. The evaluation shows that the thermal shield would likely be stopped by the core support barrel snubbers and in any event would be stopped by the core stops. The evaluation also indicates that a dropped thermal shield would not have a significant effect on core flow. We expect to be able to complete our evaluation by September 9, 1983. We will continue to keep you informed of our status.
Please feel free to contact me if you should have any question in this matter.
Very truly yours, MAINE YANKEE ATOMIC POWER COWANY jjj- /\\y$ b,
" John H. Garrity, Senior Director Nuclear Engineering and Licensing JHG/bjp cc: Dr. Thomas E. Murley Mr. Paul D. Swetland 1530L-GDW